[xmonad] update: chromium slow redraw

Due to my local xmonad --recompile breakage I had to fall back to dwm and was surprised to see that the very slow non-floating Chromium window redraw evident in XMonad since Chromium switched to Aura does NOT happen in dwm. Any idea what's different in the dwm X11 code that doesn't make Chromium window (content) redraws super visible (slow)?